Generally speaking, in order to obtain an image from an exposed silver halide photographic light-sensitive material, the light-sensitive material must be processed in a developer solution, a fixing solution, and some other solutions. Particularly, the formation of a color image needs still more processing steps. The processing solutions used in these processing steps contain various kinds of constituents, so that if water that is used for preparation of them contains metallic ions such as of calcium, magnesium, iron, the constituents react with these ions to form a precipitate or sludge, which causes clogging of the filter provided to an autoprocessor or attaches to and stain the surface of the photographic light-sensitive material being processed. Even if pure water is used in preparation of the above processing solutions in order to prevent such trouble, since the metallic ion contained in the photographic light-sensitive material is eluted in or the one from the preceding processing bath is carried in the bath during the course of its processing, it is very difficult to completely prevent the formation of a precipitate or sludge. Further, some of the constituents of such processing solutions have their oxidation or decomposition accelerated by the action of metallic ions to thereby lose effect, so if processed in such a processing solution, the light-sensitive material becomes fogged or desensitized.
To prevent such undesirable actions of metallic ions to the processing solution, the addition of a chelating agent for blocking metallic ions to the photographic processing chemical composition is proposed and now in practice used. Examples of the chelating agents include the polyphosphates such as sodium hexamethaphosphate proposed by British Patent No.520,593; the alkylidenediphosphonic acid proposed by U.S. Pat. No. 321,445; the aminopolycarboxylic acids such as aminopolymethylenephosphonic acid and ethylenediaminetetraacetic acid proposed by U.S. Pat. No. 3,201,246. However, it is the fact that even if such chelating agents are used, there still occur various shortcomings in practice, bringing about unsatisfactory results; i.e., the polyphosphate is unacceptable for practical use because of being poor in metallic ion-blocking power, particularly weak in the power against heavy-metallic ions.
The alkylidenediphosphonic acid has the disadvantage that it, when present together with both calcium and sodium ions in a certain concentration or more, forms a solid precipitate to cause a trouble in the autoprocessor. The ordinary aminopolycarboxylic acid such as ethylenediaminetetraacetic acid or the aminopolymethylenephosphonic acid such as aminotrimethylenephosphonic acid has an excellently large metallic ion blocking power, but it, when present together with metallic ions in a color developer solution containing hydroxylamine, decomposes the hydroxylamine, and the light-sensitive material, when processed in such the color developer solution, produces fog, while in a black-and-white developer solution it accelerates the oxidation of the developing agent to thereby degrade the solution's storage stability, causing a high-speed film to get fogged badly.
As has been mentioned, any one of the conventionally proposed chelating agents has some shortcomings and provides no satisfactory effect when used in photographic processing chemical compositions. Further, the replenishing amount to photographic processing solutions is compelled to be made smaller and smaller in order to live up to the social environmental demand for decreasing pollution or the economical demand for cost reduction, so that the accumulation of metallic ions such as of calcium eluted from the photographic light-sensitive material has a tendency toward increasing.
Raw materials for use in producing photographic materials also tend to be replaced by lower grade, inexpensive ones for the purpose of cost reduction; the amount of metallic ions accumulated in photographic processing solutions keeps on increasing.
Thus, the above trend has lately been coming out of control with conventional techniques.
Incidentally, in the processing of a silver halide color photographic light-sensitive material, the aforementioned aminopolycarboxylic acids as the chelating agent are widely used in large quantities in the form of metallic complex salts of the foregoing metals as bleaching agents for removing silver image in a bleaching bath and a bleach-fix bath. Examples of the metallic complex salt of the above aminopolycarboxylic acid include ferric ethylenediaminetetraacetate, ferric 1,3-propylenediaminetetraacetate and ferric diethylenetriaminepentaacetate.
Out of these bleaching agents, ferric 1,3-propylenediaminetetraacetate has a very high oxidation power, and therefore applies to a bleaching bath especially for use in the rapid processing of a high-speed silver halide color photographic light-sensitive material. However, the ferric 1,3-propylenediaminetetraacetate, because of its high oxidation power, has the disadvantage that it oxidizes the color developing agent that is carried in from the prebath in the developing process to react with the unreacted coupler contained in the light-sensitive material to thereby form a dye; i.e., it causes a so-called bleaching fog.
Ferric ethylenediaminetetraacetate is inferior in the oxidation power to ferric 1,3-propylenediaminetetraacetate, but is often used as a bleaching agent for the bleach-fix process, where both bleaching and fixing are made in a single bath for simplification and speedup of the processing process. In the bleach-fix bath, since the bleaching agent as an oxidation agent and the fixing agent, such as thiosulfate ion, as a reducing agent are present together, there occurs a phenomenon where the bleaching agent oxidizes the thiosulfate ion to thereby decompose the fixing agent into sulfur, so that a sulfite ion as a preservative is usually added to the bleach-fix bath in order to prevent the thiosulfate ion from being decomposed. However, where ferric ethylenediaminetetraacetate is used in the bleach-fix bath, the ferric complex salt's oxidation rate shifting from divalent iron to trivalent iron is so high that it always keeps its trivalent iron condition in the bleach-fix bath to keep on decomposing the sulfite ion as a preservative, resulting in the acceleration of sulfurization of the thiosulfate ion, leading to lowering of the storage stability of the bleach-fix solution.
As means to solve the above problem, JP O.P.I. (Open to Public Inspection, the same shall apply hereinafter) Nos. 149358/1984, 151154/1984 and 166977/1984 disclose techniques using ferric diethylenetriaminepentaacetate.
These techniques are certainly excellent in the solution's storage stability as compared to the bleach-fix bath that uses ferric ethylenediaminetetraacetate. However, where ferric diethylenetriaminepentaacetate is used to make color paper processing, there occurs a problem that it is liable to cause a trouble called `edge penetration` where processed color paper edges appear to be stained.
Further, the use of materials having a good spontaneous decomposability has lately been called for from the global environment protection point of view. The aforementioned ferric ethylenediaminetetraacetate and ferric diethylenetriaminepentaacetate are known to be very inferior in the spontaneous decomposability, so that the use of them is undesirable. In Germany, because the EDTA concentration in drinking water has been increasing in recent years, there is a self-imposed control move to reduce the present EDTA to half within five years.
In order to solve this problem, German Pat. DE 9,939,755 and DE 3,939,756 disclose techniques using nitrilomonopropionic acid diacetic acid (NMPDA), nitrilodipropionic acid monoacetic acid (NDPMA), and ordinary nitrilotriacetic acid (NTA) as a well spontaneously decomposable chelating agent. However, the fact that the above NMPDA and NDPMA are little decomposed is confirmed according to the decomposition proneness testing specified as a decomposability evaluation method--`amended MITI method` by the Ministry of International Trade and Industry (being recognized well-decomposable according to this method implies being decomposed fast in the natural world), so that they do not provide any radical solution to the problem.
The fact that the use of the foregoing NMPDA and NDPMA causes aforementioned bleaching fog trouble is also confirmed.
On the other hand, the NTA shows a good spontaneous decomposability in the MITI method, but its oxidation power when in the ferric complex salt form is not adequate, and therefore it is not suitable for practical use.
Accordingly, there is a strong demand for a bleaching solution having rapid desilvering characteristics without causing bleaching stain and a bleach-fix solution having excellent storage stability, causing no edge stain and having excellent decomposability.